diff --git a/libmpcodecs/sws_utils.c b/libmpcodecs/sws_utils.c
index 65b079dd84..d7500efe2e 100644
--- a/libmpcodecs/sws_utils.c
+++ b/libmpcodecs/sws_utils.c
@@ -131,6 +131,14 @@ struct SwsContext *sws_getContextFromCmdLine_hq(int srcW, int srcH,
                SWS_ACCURATE_RND | SWS_BITEXACT);
 }
 
+bool mp_sws_supported_format(int imgfmt)
+{
+    enum PixelFormat av_format = imgfmt2pixfmt(imgfmt);
+
+    return av_format != PIX_FMT_NONE && sws_isSupportedInput(av_format)
+        && sws_isSupportedOutput(av_format);
+}
+
 void mp_image_swscale(struct mp_image *dst,
                       const struct mp_image *src,
                       struct mp_csp_details *csp,
diff --git a/libmpcodecs/sws_utils.h b/libmpcodecs/sws_utils.h
index b2c55eb407..70b7d0b7fb 100644
--- a/libmpcodecs/sws_utils.h
+++ b/libmpcodecs/sws_utils.h
@@ -1,6 +1,7 @@
 #ifndef MPLAYER_SWS_UTILS_H
 #define MPLAYER_SWS_UTILS_H
 
+#include <stdbool.h>
 #include <libswscale/swscale.h>
 
 struct mp_image;
@@ -22,8 +23,12 @@ struct SwsContext *sws_getContextFromCmdLine_hq(int srcW, int srcH,
                                                 int dstFormat);
 int mp_sws_set_colorspace(struct SwsContext *sws, struct mp_csp_details *csp);
 
-void mp_image_swscale(struct mp_image *dst, const struct mp_image *src,
-                      struct mp_csp_details *csp, int my_sws_flags);
+bool mp_sws_supported_format(int imgfmt);
+
+void mp_image_swscale(struct mp_image *dst,
+                      const struct mp_image *src,
+                      struct mp_csp_details *csp,
+                      int my_sws_flags);
 
 #endif /* MP_SWS_UTILS_H */
 
diff --git a/sub/draw_bmp.c b/sub/draw_bmp.c
index 315e52dfdd..9945a8fc89 100644
--- a/sub/draw_bmp.c
+++ b/sub/draw_bmp.c
@@ -464,6 +464,9 @@ void mp_draw_sub_bitmaps(struct mp_draw_sub_cache **cache, struct mp_image *dst,
     float yuv2rgb[3][4];
     float rgb2yuv[3][4];
 
+    if (!mp_sws_supported_format(dst->imgfmt))
+        return;
+
     if (cache && !*cache)
         *cache = talloc_zero(NULL, struct mp_draw_sub_cache);